Over a half billion individuals worldwide are infected with herpes simplex virus type 1 and/or type 2 (HSV-1 & HSV-2), which cause genital herpes. Most HSV-seropositive individuals are asymptomatic (ASYMP) and never have any recurrent herpetic disease. In contrast, a small proportion is symptomatic (SYMP), with frequent, often lifelong bouts of recurrent herpetic disease, a result of reactivation of latent HSV from sensory neurons of the dorsal root ganglia (DRG). Our long-term goal is to develop an immunotherapeutic vaccine to prevent virus reactivation from latency and protect against recurrent genital herpes disease. The most recent vaccine clinical trials that used HSV-2 glycoprotein D (gD) failed to protect despite inducing strong HSV-specific neutralizing antibodies. This proposal emphasizes two major gaps in knowledge: (1) The need to induce cell-mediated immune responses (in addition to humoral responses) for better protection. (2) The need to identify novel herpes T cell antigens (Ags) to be incorporated into next-generation HSV vaccines. A critical role for HSV- specific sensory ganglia-resident CD8+ T cells in aborting HSV reactivation has been established, and the involvement of CD4+ T cells is gaining wider acceptance. Paradoxically, HSV-specific genital tract (GT)- resident CD4+ and CD8+ T-cells are also involved in herpes pathogenicity. The Ag specificities of protective and pathogenic CD4+ and CD8+ T-cells remain to be elucidated. Our recent published and preliminary data demonstrate that: (A) CD4+ and CD8+ T-cells from HSV-seropositive SYMP and ASYM individuals differ in their HSV Ag-specificities, phenotype, and function. (B) Immunization of novel susceptible Human Leukocyte Antigen- (HLA-) A/DR double transgenic mice (HLA Tg mice) with ASYMP Ags, but not SYMP Ags, induced a strong T cell-dependent protective immunity against genital herpes. Building on the above published and preliminary data in both humans and HLA Tg mice, we hypothesize that: (1) CD4+ and CD8+ T-cells specific to HSV Ags can be either protective or pathogenic, and (2) A vaccine strategy that can boost the number and/or function of DRG-resident protective CD4+ and CD8+ T cells will prevent or reduce virus reactivation and, hence, protect against recurrent genital herpes. Our Specific Aims are: Aim 1: To confirm the hypothesis that there is a set of HSV Ags that are recognized mostly by CD4+ and CD8+ T cells from ASYMP individuals and a different set of Ags that are recognized mostly by CD4+ and CD8+ T cells from SYMP individuals. Aim 2: To test the hypothesis that immunization of HLA double Tg mice with immunodominant ASYMP Ags, but not with SYMP Ags, will induce DRG-resident CD4+ and CD8+ T cells, and protect against genital herpes infection and disease. Successful completion of the proposed work should help build a strong foundation toward developing an effective genital herpes vaccine.